Optical sensing methods and apparatus for detecting a color of a marking substance

ABSTRACT

Marking devices for dispensing a marking substance on the ground and marking methods are provided. The marking devices and marking methods use one or more detection mechanisms to detect one or more characteristics of the marking substance. In some embodiments, the detection mechanism may be, but is not limited to, an optical sensor, an olfactory sensor, a weight sensor, a switch device, and any combination thereof. The one or more detection mechanisms may provide, for example, the capability to: (1) determine the type of marking substance that is installed in the marking device; (2) determine in advance of or during a marking operation the amount of marking substance within the marking dispenser; and (3) determine when the marking dispenser is becoming empty.

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit, under 35 U.S.C. §120, as a continuation(CON) of U.S. Non-provisional application Ser. No. 12/429,947, entitled“Marker Detection Mechanisms for Use in Marking Devices and Methods ofUsing Same” filed Apr. 24, 2009.

Application Ser. No. 12/429,947 in turn claims the benefit, under 35U.S.C. §119(e), of U.S. Provisional Application Ser. No. 61/079,518,entitled “Paint Detection Mechanisms for Use in Marking Devices andMethods of Making Same,” filed Jul. 10, 2008.

Each of the above-referenced applications is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to the field of marking devicesfor placing marks on the ground. In particular, the present inventionrelates to marker detection mechanisms for use in marking devices andmethods of using same.

BACKGROUND

Marking paint, such as inverted marking spray paint (also known as“upside down paint”), may be used by land surveyors, undergroundfacility locate technicians, or anyone that has a need to mark alocation on the ground. Marking paint may be dispensed onto the groundusing marking devices, such as paint marking wands, applicators, and/orwheels.

In many marking applications, a specified marking paint color may berequired for identifying a particular facility or entity. For example,once located, an underground power line may be marked with one color, anunderground telephone line may be marked with another color, anunderground gas line may be marked with yet another color, and so on.Paint durability and/or ease of removal of the marking paint may also beimportant. These marking paint characteristics may vary depending on thesurface on which the marking paint is applied (e.g., pavement, grass,gravel, and so on). Consequently, marking paint may be formulated tovary in accordance with durability and/or ease of removal specificationsfor different surfaces and uses. For example, municipalities may requirethat marking paint on streets and sidewalks fade away within a specifiedperiod of time. Therefore, it may be beneficial to develop mechanismsfor ensuring, for example, that the proper color and/or formulation ofmarking paint is being used and/or has been used.

In addition, certain inefficiencies may exist in marking applicationswhen the user of the marking device is unaware of the amount of markingpaint contained within a paint dispenser. For example, if a largemarking operation is begun with a partially filled paint dispenser, thepaint dispenser may become empty before the marking operation iscomplete. Consequently, the marking operation may be interrupted whilethe user retrieves another full paint dispenser to replace the emptypaint dispenser and resumes the marking operation. Therefore, it may bebeneficial to develop ways for the user and/or remote supervisor to knowand record the type and amount of marking paint present in the markingdevice, the corresponding paint marking distance and/or when the paintdispenser is becoming empty.

Accordingly, approaches are needed for automatically determining thecharacteristics, such as color and durability, of marking paint used ina marking operation, such as an underground facility locate operation;for monitoring the amount of marking paint present in the markingdispenser and/or for determining when the marking dispenser is becomingempty.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a marking apparatus isprovided to mark the presence or absence of an underground facility in adig area. The marking apparatus comprises: a housing configured toenable dispensing of a marking substance onto the ground for marking thepresence or absence of an underground facility in a dig area; a markingdispenser holder affixed to the housing to hold at least one markingdispenser; an actuator to cause dispensing of the marking substance fromthe marking dispenser onto the ground in the dig area, in a markingoperation, to mark the presence or absence of an underground facility;at least one marking substance detection mechanism to detect one or morecharacteristics of the marking substance dispensed from the markingdispenser and to provide detector information representative of the oneor more characteristics; and a processing device to generate outputinformation in response to the detector information, the outputinformation representing the one or more characteristics of the markingsubstance.

According to a second aspect of the invention, a method is provided forperforming a marking operation for marking the presence or absence of anunderground facility in a dig area using a marking apparatus that holdsat least one marking dispenser. The method comprises: dispensing amarking substance from the marking dispenser onto the ground in the digarea, in a marking operation, to mark the presence or absence of anunderground facility, in response to activation of the markingdispenser; detecting one or more characteristics of the markingsubstance dispensed from the marking dispenser and providing detectorinformation representative of the one or more characteristics; andgenerating output information in response to the detector information,the output information representing the one or more characteristics ofthe marking substance.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the present invention, the drawings showaspects of one or more embodiments of the present invention. However, itshould be understood that the present invention is not limited to theprecise arrangements and instrumentalities shown in the drawings,wherein:

FIG. 1 is a schematic diagram of a marking device that includes adetection mechanism, and a block diagram of the control electronics ofthe marking device;

FIG. 2 is a schematic diagram of a marking device that includes anoptical sensor;

FIG. 3 is a flow diagram of an embodiment of a method of using themarking device that includes the optical sensor for identifying thecomposition and/or type of marking substance in the marking dispenser;

FIG. 4 is a schematic diagram of a marking device that includes anolfactory sensor;

FIG. 5 is a flow diagram of a method of using the marking device thatincludes the olfactory sensor for identifying the composition and/ortype of marking substance in the marking dispenser;

FIG. 6 is a flow diagram of a method of using a detection mechanism in asystem for processing marking substance information;

FIG. 7 is a schematic diagram of a marking device that includes a weightsensor;

FIG. 8 is a flow diagram of a method of using the marking device thatincludes the weight sensor for determining the amount of markingsubstance in the marking dispenser; and

FIG. 9 is a schematic diagram of a marking device that includes anout-of-paint sensor.

DETAILED DESCRIPTION

The invention relates to marking devices for dispensing a markingsubstance on the ground and to marking methods. The marking devices andmarking methods use one or more detection mechanisms to detect one ormore characteristics of the marking substance. In some embodiments ofthe invention, the detection mechanism may be, but is not limited to, anoptical sensor, an olfactory sensor, a weight sensor, a switch device,and any combinations thereof. The one or more detection mechanisms mayprovide, for example, the capability to: (1) determine the type ofmarking substance that is installed in the marking device; (2) determinein advance of or during a marking operation the amount of markingsubstance within the marking dispenser; and (3) determine when themarking dispenser is becoming empty.

FIG. 1 is a schematic diagram of a marking device 100 that includes atleast one detection mechanism. The marking device 100 is also referredto herein as a “marking apparatus.” FIG. 1 also shows a block diagram ofthe control electronics of marking device 100. In particular, markingdevice 100 may include a detection mechanism for detecting the type ofmarking substance, detecting the amount of marking substance in themarking dispenser, and/or detecting when the marking dispenser isbecoming empty.

Marking device 100 may include a shaft 110, a handle 114 at one end ofshaft 110, and a marking dispenser holder 118 for holding a markingdispenser 122 at the end of shaft 110 that is opposite handle 114.Additionally, marking device 100 may include a trigger 126 for actuatinga spray nozzle 130 of marking dispenser 122 to dispense a markingsubstance 134 onto the target of a marking operation, such as theground. Marking dispenser 122 may be an aerosol canister that contains aquantity of a marking substance 134. Marking substance 134 may be, forexample, marking paint, marking chalk, marking dye, marking powder, andthe like. In one example, marking dispenser 122 may be an aerosolcanister that contains marking paint, such as commercially availablemarking paint. Marking device 100 may be configured to hold a singlemarking dispenser or more than one marking dispenser.

A basic marking operation of marking device 100 may be described asfollows. A user, such as a locate technician in, for example, anunderground facility locate application, loads a marking dispenser 122that contains a quantity of marking substance 134 into marking dispenserholder 118. The user grasps handle 114 of marking device 100 and aimsnozzle 130 of marking dispenser 122 at the intended target. The userthen pulls trigger 126, which may be mechanically coupled to spraynozzle 130 of marking dispenser 122, in order to dispense markingsubstance 134 in a specified pattern on the intended target, such as theground. For example, marking device 100 may be used to mark lines,arrows, geometric shapes, numbers, letters, words, and any combinationsthereof on the ground.

Marking device 100 further includes at least one marking substancedetection mechanism 140 and control electronics 144, as described below.In some embodiments, marking device 100 is configured for mounting asingle marking dispenser and includes at least one detection mechanism.In other embodiments, marking device 100 is configured for mounting oneor more marking dispensers and includes one or more detection mechanismsfor each marking dispenser. In further embodiments, marking device 100includes two or more detection mechanisms of the same or differenttypes.

Marking substance detection mechanism 140 may include any sensor ordevice that provides information about a characteristic of markingsubstance 134, such as color or formulation, durability and/or amount ofthe marking substance 134 in marking dispenser 122. For example,detection mechanism 140 may include, but is not limited to, opticalsensing devices, weight sensing devices, olfactory sensing devices,switching devices, other mechanical/electrical components, and anycombinations thereof. The location of the detection mechanism 140relative to marking dispenser 122 may vary depending on the type orfunction of the sensing device. The detection of marking substance 134may be direct, as in the case of an optical sensor, or may be indirect,as in the case of a weight sensor that senses the weight of markingdispenser 122 and marking substance 134. Non-limiting examples ofdetection mechanism 140 are described in more detail with reference toFIGS. 2 through 9.

Control electronics 144 is provided for, among other purposes,communicating with and processing information from detection mechanism140. Control electronics 144 may include a processor 150, a userinterface 152, a storage device 154, a detection algorithm 156, acommunications interface 158, and a power source 160. Detectionalgorithm 156 may be implemented as a software module executed byprocessor 150 and stored in storage device 154, or as a separatecoprocessor controlled by processor 150. Power source 160 of controlelectronics 144 may be, for example, one or more rechargeable ornon-rechargeable batteries.

Processor 150 may be any general purpose or special purpose processor,controller, microcontroller, or digital signal processor (DSP) devicefor managing the overall control of marking device 100. Processor 150may be a programmable processor that is capable of executing programinstructions of, for example, detection algorithm 156. Additionally,processor 150 manages the communication between trigger 126, detectionmechanism 140, user interface 152, storage device 154, and detectionalgorithm 156.

User interface 152 may be, for example, any visual and/or audible devicethat may be used in order to provide feedback (depending on the type andfunction of detection mechanism 140) to the user of the marking device100. For example, user interface 152 may include visual devices, such asone or more light-emitting diode (LED) devices and/or a display device,and one or more audible devices, such as a buzzer, a beeper, a speaker,and the like. User interface 152 may also include one or more inputdevices, such as a touch screen or a keypad, to receive user inputs.

In one example, selected information, including but not limited todetected information from detection mechanism 140 and/or informationgenerated by detection algorithm 156, may be stored locally in storagedevice 154. Non-limiting examples of information that may be stored instorage device 154 are described in more detail with reference to FIGS.2 through 9. Storage device 154 may be any volatile or non-volatile datastorage device, such as, but not limited to, a random access memory(RAM) device and a removable memory device (e.g., a USB flash drive).Optionally, storage device 154 is not included in control electronics144. Instead, embedded memory (not shown) within processor 150 may beused for caching information during the operation of marking device 100.

Detection algorithm 156 may process and interpret information receivedfrom detection mechanism 140 and then issue a response, if necessary.The functions of detection algorithm 156 may vary depending on the typeand function of detection mechanism 140. For example, detectionalgorithm 156 may process and interpret optical sensor information,weight sensor information, olfactory sensor information, switchinformation, and any combinations thereof. The general operations ofdetection algorithm 156 may include, but are not limited to: (1) readingreference detection information; (2) reading measured detectioninformation from detection mechanism 140; (3) comparing the measureddetection information from detection mechanism 140 with the referencedetection information; (4) determining whether there is a match betweenthe measured detection information from detection mechanism 140 and thereference detection information; and (5) generating output informationthat is based on the comparison and/or specified rules. Non-limitingexamples of the operation of detection algorithm 156 in combination withdetection mechanism 140 are described in more detail with reference toFIGS. 2 through 9.

Communications interface 158 may be any wired and/or wireless interfaceby which data is transmitted from marking device 100 to an external orremote device, such as a remote computing device. The remote computingdevice may be, for example, a computer in the user's vehicle and/or aserver at a central location. Examples of wired interfaces may include,but are not limited to, universal serial bus (USB) ports, RS232connectors, RJ45 connectors, and any combinations thereof. Examples ofwireless interfaces may include, but are not limited to, Bluetooth®technology and IEEE 802.11 technology. Information received fromdetection mechanism 140 may be transmitted in real time or non-real timefrom marking device 100 via communications interface 158 with or withoutbeing stored locally in storage device 154 and with or without beingprocessed.

In one example, detection mechanism 140 and control electronics 144 maybe integrated into any commercially available marking device to formmarking device 100. Alternatively, detection mechanism 140 and controlelectronics 144 may be integrated into the marking systems that aredescribed in U.S. patent application Ser. No. 11/696,606, filed Apr. 4,2007 and published Oct. 9, 2008 as Publication No. 2008/0245299,entitled “Marking system and method”; and U.S. patent application Ser.No. 11/685,602, filed Mar. 13, 2007 and published Sep. 19, 2008 asPublication No. 2008/0228294, entitled “Marking system and method withlocation and/or time tracking,” both of which are incorporated byreference herein in their entirety.

FIG. 2 is a schematic diagram of the lower end of marking device 100,including a detection mechanism in the form of an optical sensor 210.Optical sensor 210 is mounted near marking dispenser holder 118 suchthat there is a “line of sight” between optical sensor 210 and markingsubstance 134 as it is dispensed from spray nozzle 130 of markingdispenser 122. An overspray guard 212 may be utilized to limit buildupof marking substance 134 on the optical window of optical sensor 210.

In one example, optical sensor 210 may be a spectrometer (or reflectancespectrometer) device, which is an optical instrument that is used tomeasure properties of light over a specific portion of theelectromagnetic spectrum. Spectrometers are typically used to performspectroscopic analysis to identify materials. In a marking applicationthat uses marking device 100, the spectrometer (e.g., optical sensor210) is used to perform spectroscopic analysis to identify markingsubstance 134, which may be one of a variety of colors and formulationsof marking substance 134. Commercially available low power, compactspectrometer devices may be suitable for use as optical sensor 210 ofmarking device 100. The output signal from optical sensor 210 depends onthe type of optical sensor used and may be a digital or analog signal.When the optical sensor 210 is a spectrometer, the output signal fromoptical sensor 210 represents the spectrum of marking substance 134. Theoutput signal of optical sensor 210 may be utilized directly todetermine the characteristics of the marking substance or may bepreprocessed by processor 150 to simplify analysis. For example,processor 150 may convert the measured spectral information to anumerical value for comparison with the values in Table 1 below.

Optionally, a light source (not shown) may be utilized in combinationwith optical sensor 210 to provide a consistent light intensity withinthe field of view of optical sensor 210. The light source may be anylight source, such as, but not limited to, a white or colored lightsource, a laser source, an ultraviolet (UV) light source, and the like.Optionally, unique optical markers may be added to the chemicalformulations of compositions and/or types of marking substances 134 inorder to provide a unique detectable spectrum for the differentcompositions and/or types of marking substances 134. In one example, ablack light may be used in combination with optical sensor 210 to detectUV markers that have been added to the chemical formulations of markingsubstances 134.

In this embodiment, the spectral signature of each of the possiblecolors, types, durabilities, manufacturers, and the like of markingsubstances 134 are predetermined and stored, for example, in storagedevice 154. In a learning mode, the optical sensor 210 may be used tomeasure the spectrum information of each composition and/or type ofmarking substance 134 of interest. The spectrum measurements of thedifferent compositions and/or types of marking substances 134 may bestored in order to provide a set of reference spectral signatures forlater comparison with measured spectral signatures. Then, the sameoptical sensor 210 is used to measure the spectral signatures of markingsubstances dispensed by the marking device. In this approach, the effectof differences among optical sensors 210 is eliminated. In anotherapproach, spectral signatures are measured by a reference optical sensorto provide reference spectral signatures, and the reference spectralsignatures are provided, such as by downloading, to one or more markingdevices. The measured spectral signature of marking substance 134 iscompared to the reference spectral signatures to identify the markingsubstance 134 being dispensed.

The marking device 100 may detect, among other characteristics, thedurability of marking substance 134. Such durability may be evaluated bycomparison with known criterion pertaining to location and environmentof the intended use of marking device 100. In the event that thedurability of marking substance 134 is found to be inappropriate for theknown criterion, a notification is generated for the user to replacemarking dispenser 122. In other embodiments, such notification may besent to supervisory and other appropriate personnel throughcommunication media such as e-mail, SMS, RSS, internet/intranetdashboards, and the like.

Table 1 below shows an example of reference spectral signatureinformation that may be stored in storage device 154. The informationcorrelates specified marking substances 134 to predetermined spectralsignatures.

TABLE 1 Marking Substance vs. Expected Spectral Signature ApprovedMarking Optical Sensor Spectral Brand Color Durability Use ReadingSignature None Clear N/A N/A 0.0 0000 Brand #1 Yellow High Gas 2.0 0001Brand #2 Yellow High Gas 4.0 0002 Brand #1 Yellow Medium Gas 6.0 0003Brand #2 Yellow Medium Gas 8.0 0004 Brand #1 Yellow Low Gas 10.0 0005Brand #2 Yellow Low Gas 12.0 0006 Brand #1 Blue High Water 14.0 0007Brand #2 Blue High Water 16.0 0008 Brand #1 Blue Medium Water 18.0 0009Brand #2 Blue Medium Water 20.0 0010 Brand #1 Blue Low Water 22.0 0011Brand #2 Blue Low Water 24.0 0012 Brand #1 Orange High Tel/CATV 26.00013 Brand #2 Orange High Tel/CATV 28.0 0014 Brand #1 Orange MediumTel/CATV 30.0 0015 Brand #2 Orange Medium Tel/CATV 32.0 0016 Brand #1Orange Low Tel/CATV 34.0 0017 Brand #2 Orange Low Tel/CATV 36.0 0018Brand #1 Green High Sewer 38.0 0019 Brand #2 Green High Sewer 40.0 0020Brand #1 Green Medium Sewer 42.0 0021 Brand #2 Green Medium Sewer 44.00022 Brand #1 Green Low Sewer 46.0 0023 Brand #2 Green Low Sewer 48.00024 Brand #1 Red High Power 50.0 0025 Brand #2 Red High Power 52.0 0026Brand #1 Red Medium Power 54.0 0027 Brand #2 Red Medium Power 56.0 0028Brand #1 Red Low Power 58.0 0029 Brand #2 Red Low Power 60.0 0030

Referring to Table 1, spectral signature 0000 is an entry thatcorrelates to no marking substance 134 being dispensed from markingdispenser 122. By contrast, all other spectral signatures (e.g.,0001-0030) are spectral signatures of respective colors or types ofmarking substances 134. Spectral signature 0000 is useful to detect thata marking dispenser 122 is becoming empty or is malfunctioning during amarking operation. For example, processor 150 may detect that trigger126 is being pulled and at the same time optical sensor 210 may detect aspectral signature that substantially matches spectral signature 0000.This indicates that marking dispenser 122 is becoming empty orsubstantially empty of marking substance 134, or is malfunctioning. Whentrigger 126 is not being pulled, the spectral data that is received fromoptical sensor 210 may be ignored.

An aspect of this embodiment is that optical sensor 210 may be used for:(1) detecting the characteristics of marking substance 134, and (2)detecting that marking dispenser 122 is becoming empty or substantiallyempty, or is malfunctioning.

In this embodiment, detection algorithm 156 may process and interpretspectral information that is received from optical sensor 210, and thengenerate an appropriate response, if any. Details of the operation ofmarking device 100 including optical sensor 210 are described withreference to FIG. 3.

Referring now to FIG. 3, a flow diagram of a method 300 is shown. Themethod uses marking device 100 which includes optical sensor 210 foridentifying the composition and/or type of marking substance in themarking dispenser. Method 300 may include, but is not limited to, thefollowing acts. Additionally, the acts of method 300 are not limited tothe following order.

In act 312, processor 150, executing detection algorithm 156, sensesthat trigger 126 is being pulled by the user of marking device 100 andreads the measured spectral information (via optical sensor 210) of themarking substance 134 that is being dispensed from marking device 100.

In act 314, detection algorithm 156 determines whether marking dispenser122 is empty or substantially empty. For example, detection algorithm156 determines whether the information received from optical sensor 210substantially matches spectral signature 0000 of Table 1. If yes, method300 proceeds to act 316. If no, method 300 proceeds to act 318.

In act 316, processor 150, executing detection algorithm 156, generatesoutput information to the user of marking device 100 that markingdispenser 122 is becoming empty or is empty and performs any otherdesired tasks, such as, but not limited to, deactivating the trigger,transmitting a notification in real time to a remote server that markingdispenser 122 is becoming empty or is empty (i.e., a real-time alert toa supervisor that a user in the field may be spraying but no paint isbeing dispensed), and so on. For example, an OUT OF PAINT message may bedisplayed to the user via user interface 152 and trigger 126 may bedeactivated, after which method 300 ends.

If the marking dispenser is not empty, method 300 proceeds to act 318,wherein detection algorithm 156 compares the measured spectralinformation received from optical sensor 210 (before or afterpreprocessing by processor 150) with the stored spectral signatureinformation, for example, of Table 1. More specifically, detectionalgorithm 156 compares the measured spectral information received fromoptical sensor 210 with spectral signatures 0001 through n of Table 1 inorder to determine a match. For example, a value of about 10 fromoptical sensor 210 corresponds to spectral signature 0005, a value ofabout 46 from optical sensor 210 corresponds to spectral signature 0023,a value of about 54 from optical sensor 210 corresponds to spectralsignature 0027, and so on. Table 1 can be stored during execution ofmethod 300 in a high speed memory associated with processor 150.

In act 320, based on the comparison of act 318, if a match is foundbetween the measured spectral information from optical sensor 210 and atleast one spectral signature of Table 1, method 300 proceeds to act 322.However, based on the comparison of act 318, if no match is foundbetween the measured spectral information from optical sensor 210 and atleast one spectral signature of Table 1, method 300 proceeds to act 324.

In act 322, processor 150, executing detection algorithm 156, generatesoutput information to the user of marking device 100 indicating thecharacteristics of marking substance 134 that is installed in markingdevice 100. For example, if optical sensor 210 detects spectralinformation that substantially matches spectral signature 0009, thebrand, color, durability, and approved usage that correlates withspectral signature 0009 (e.g., Brand #1, blue, medium durability, andwater line) may be displayed to the user via user interface 152. Method300 returns to act 312.

In act 324, processor 150, executing detection algorithm 156, generatesoutput information to the user of marking device 100 that is based onnon-matching of spectral information. For example, if optical sensor 210detects spectral information that does not substantially match anyspectral signature of Table 1, an UNKNOWN PAINT message may be displayedto the user via user interface 152 and, optionally, trigger 126 may bedeactivated. Optionally, a notification may be transmitted to a remoteserver that the marking substance 134 in marking dispenser 122 does notmatch any expected spectral signatures (i.e., a real-time alert to asupervisor that a user in the field may be spraying an unknown markingsubstance), after which method 300 ends.

As described above, marker information may be provided to the user viauser interface 152 in response to the measured spectral information. Forexample, the brand, color, durability and approved usage of the markingsubstance may be displayed to the user. The user can be prompted toverify that the detected characteristics of the marking substance areappropriate for the marking operation being performed. If yes, the usercan enable the marking operation to proceed. If not, the user may signalthe marking device to wait while the marking dispenser is changed orother required actions are taken. The processor 150 may also provide anout-of-paint message or an unknown paint message, depending on themeasured spectral information. In other embodiments, the markingoperation may be controlled automatically in response to the measuredspectral information. For example, further dispensing of the markingsubstance may be inhibited if the characteristics of the markingsubstance detected by optical sensor 210 do not match preprogrammedparameters of the marking operation, such as underground utility type.In further embodiments, the measured spectral information, before orafter preprocessing by processor 150, may be stored in storage device154 and/or transmitted to a remote device for offline processing.

The optical sensor 210 is described above as a spectrometer fordetecting spectral characteristics of the marking substance. It will beunderstood that a variety of different optical sensing configurationscan be utilized within the scope of the present invention. In theembodiment of FIG. 2, optical sensor 210 senses reflected light frommarking substance 134. In some embodiments, a light source can beutilized to illuminate the marking substance 134. The light source maybe positioned adjacent to optical sensor 210 to permit sensing ofreflected light from marking substance 134. In other embodiments, thelight source can be positioned on the opposite side of marking substance134 from optical sensor 210, so that light emitted by the light sourceis transmitted through marking substance 134 and is sensed by opticalsensor 210. The light source can have broad band or narrow band spectralcharacteristics. The light source can be a DC source or can be pulsed orotherwise modulated to improve detection capability. The optical sensor210 itself can have broad band or narrow band characteristics.Furthermore, optical fibers can be used to carry light to and frommarking substance 134. The characteristics of optical sensor 210 andother optical components depends on the characteristics of the markingsubstance 134 to be detected and the conditions under which the markingdevice will be used.

FIG. 4 is a schematic diagram of the lower end of marking device 100,including a detection mechanism in the form of an olfactory sensor 410.Olfactory sensor 410 has an input line 412 mounted near markingdispenser holder 118, so that one end of input line 412 is in closeproximity to marking substance 134 as it is dispensed from spray nozzle130 of marking dispenser 122.

Olfaction refers to the sense of smell, and an olfactory sensor is adevice for mimicking human olfaction. An olfactory sensor may also beknown as an electronic nose, e-nose, ENose, artificial nose, and so on.Input line 412 may be a hollow tube that is used to direct vapor emittedby marking substance 134 to the detection system of olfactory sensor410. Guard 212 may be provided. In this embodiment, guard 212 may bedesigned as a wind guard to limit wind interference with olfactorysensing of marking substance 134.

The detection system of an olfactory sensor is the “reactive” portion ofthe instrument. When in contact with volatile compounds, the sensorsreact, which means they experience a change of electrical properties.Most olfactory sensors use sensor arrays that react to volatilecompounds on contact. For example, the adsorption of volatile compoundson the sensor surface causes a physical change of the sensor. A specificresponse is recorded by the electronic interface thereof fortransforming the physical change to an electrical signal. The morecommonly used olfactory sensors include metal oxide semiconductors(MOS), conducting polymers (CP), quartz crystal microbalance, surfaceacoustic wave (SAW), and field effect transistors (MOSFET). Commerciallyavailable low power, compact olfactory sensors may be suitable for useas olfactory sensor 410 of marking device 100. The signal provided byolfactory sensor 410 depends on the type of olfactory sensor used andmay be a digital or analog signal. The output signal of olfactory sensor410 may be utilized directly by processor 150 to determine thecharacteristics of marking substance 134 or may be preprocessed tosimplify analysis. For example, processor 150 may convert the measuredolfactory information to a numerical value for comparison with thevalues in Table 2 below.

In this embodiment, the olfactory signature of each of the possiblecolors, types, manufacturers, and so on of marking substances 134 arepredetermined and stored, for example, in storage device 154.Optionally, certain unique fragrances may be added to the chemicalformulations of each composition and/or type of marking substance 134 inorder to provide a unique detectable scent for each differentcomposition and/or type of marking substance 134.

In a learning mode, the olfactory sensor 410 may be used to measure theolfactory information of each composition and/or type of markingsubstance 134 of interest. The olfactory measurements of the differentcompositions and/or types of marking substances 134 may be stored inorder to provide a set of reference olfactory signatures for latercomparison with measured olfactory signatures. Then, the same olfactorysensor 410 is used to measure the olfactory signatures of markingsubstances dispensed by the marking device. In this approach, the effectof differences among olfactory sensors 410 is eliminated. In anotherapproach, olfactory signatures are measured by a reference olfactorysensor to provide reference olfactory signatures, and the referenceolfactory signatures are provided, such as by downloading, to one ormore marking devices. The detected olfactory signature of markingsubstance 134 is compared to the reference olfactory signatures toidentify the marking substance 134 being dispensed.

Table 2 below shows an example of reference olfactory signatureinformation that may be stored in storage device 154. The informationcorrelates specified marking substances 134 to predetermined olfactorysignatures.

TABLE 2 Marking Substance vs. Expected Olfactory Signature ApprovedOlfactory Marking Sensor Olfactory Brand Color Durability Use ReadingSignature None Clear N/A N/A 0.0 0000 Brand #1 Yellow High Gas 2.0 0001Brand #2 Yellow High Gas 4.0 0002 Brand #1 Yellow Medium Gas 6.0 0003Brand #2 Yellow Medium Gas 8.0 0004 Brand #1 Yellow Low Gas 10.0 0005Brand #2 Yellow Low Gas 12.0 0006 Brand #1 Blue High Water 14.0 0007Brand #2 Blue High Water 16.0 0008 Brand #1 Blue Medium Water 18.0 0009Brand #2 Blue Medium Water 20.0 0010 Brand #1 Blue Low Water 22.0 0011Brand #2 Blue Low Water 24.0 0012 Brand #1 Orange High Tel/CATV 26.00013 Brand #2 Orange High Tel/CATV 28.0 0014 Brand #1 Orange MediumTel/CATV 30.0 0015 Brand #2 Orange Medium Tel/CATV 32.0 0016 Brand #1Orange Low Tel/CATV 34.0 0017 Brand #2 Orange Low Tel/CATV 36.0 0018Brand #1 Green High Sewer 38.0 0019 Brand #2 Green High Sewer 40.0 0020Brand #1 Green Medium Sewer 42.0 0021 Brand #2 Green Medium Sewer 44.00022 Brand #1 Green Low Sewer 46.0 0023 Brand #2 Green Low Sewer 48.00024 Brand #1 Red High Power 50.0 0025 Brand #2 Red High Power 52.0 0026Brand #1 Red Medium Power 54.0 0027 Brand #2 Red Medium Power 56.0 0028Brand #1 Red Low Power 58.0 0029 Brand #2 Red Low Power 60.0 0030

Referring to Table 2, olfactory signature 0000 is an entry thatcorrelates to no marking substance 134 being dispensed from markingdispenser 122. By contrast, all other olfactory signatures (e.g.,0001-0030) are olfactory signatures of respective colors or types ofmarking substances 134. Olfactory signature 0000 is useful to detectwhen a marking dispenser 122 is becoming empty or is malfunctioningduring a marking operation. For example, processor 150 may detect thattrigger 126 is being pulled and at the same time, olfactory sensor 410may detect an olfactory signature that substantially matches olfactorysignature 0000. This indicates that marking dispenser 122 is becomingempty or substantially empty of marking substance 134, or ismalfunctioning. When trigger 126 is not being pulled, the olfactory datathat is returned from olfactory sensor 410 may be ignored.

An aspect of this embodiment is that olfactory sensor 410 may be usedfor: (1) detecting the characteristics of marking substance 134, and (2)detecting when marker dispenser 122 is becoming empty or substantiallyempty, or is malfunctioning.

In this embodiment, detection algorithm 156 may process and interpretolfactory information that is received from olfactory sensor 410 andthen generate an appropriate response, if any. Details of the operationof marking device 100 including olfactory sensor 410 are described withreference to FIG. 5.

Referring now to FIG. 5, a flow diagram of a method 500 is shown. Themethod uses marking device 100 which includes olfactory sensor 410 foridentifying the composition and/or type of marking substance in themarking dispenser. Method 500 may include, but is not limited to, thefollowing acts. Additionally, the acts of method 500 are not limited tothe following order.

In act 512, processor 150, executing detection algorithm 156, sensesthat trigger 126 is being pulled by the user of marking device 100 andreads the measured olfactory information (via olfactory sensor 410) ofthe marking substance 134 that is being dispensed from marking device100.

In act 514, detection algorithm 156 determines whether marking dispenser122 is becoming empty or substantially empty. For example, detectionalgorithm 156 determines whether the information received from olfactorysensor 410 substantially matches olfactory signature 0000 of Table 2. Ifyes, method 500 proceeds to act 516. If no, method 500 proceeds to act518.

In act 516, processor 150, executing detection algorithm 156, generatesoutput information to the user of marking device 100 that markingdispenser 122 is becoming empty or is empty and performs any otherdesired tasks, such as, but not limited to, deactivating the trigger,transmitting a notification in real time to a remote server that markingdispenser 122 is becoming empty or is empty (i.e., a real-time alert toa supervisor that a user in the field may be spraying but no paint isbeing dispensed), and so on. For example, an OUT OF PAINT message may bedisplayed to the user via user interface 152 and trigger 126 may bedeactivated, after which method 500 ends.

If the marking dispenser is not empty, method 500 proceeds to act 518,wherein detection algorithm 156 compares the measured olfactoryinformation received from olfactory sensor 410 (before or afterpreprocessing by processor 150) with the stored olfactory signatureinformation, for example, of Table 2. More specifically, detectionalgorithm 156 compares the measured olfactory information received fromolfactory sensor 410 with olfactory signatures 0001 through n of Table 2in order to determine a match. For example, a value of about 4 fromolfactory sensor 410 corresponds to olfactory signature 0002, a value ofabout 22 from olfactory sensor 410 corresponds to olfactory signature0011, a value of about 60 from olfactory sensor 410 corresponds toolfactory signature 0030, and so on. Table 2 can be stored duringexecution of method 500 in a high speed memory associated with processor150.

In act 520, based on the comparison of act 518, if a match is foundbetween the measured olfactory information from olfactory sensor 410 andat least one olfactory signature of Table 2, method 500 proceeds to act522. However, based on the comparison of act 518, if no match is foundbetween the measured olfactory information from olfactory sensor 410 andat least one olfactory signature of Table 2, method 500 proceeds to act524.

In act 522, processor 150, executing detection algorithm 156, generatesoutput information to the user of marking device 100 indicating thecharacteristics of marking substance 134 that is installed in markingdevice 100. For example, if olfactory sensor 410 returns olfactoryinformation that substantially matches olfactory signature 0009, thebrand, color, durability, and approved usage that correlates witholfactory signature 0009 (e.g., Brand #1, blue, medium durability, andwater line) may be displayed to the user via user interface 152. Method500 returns to act 512.

In act 524, processor 150, executing detection algorithm 156, generatesoutput information to the user of marking device 100 that is based onnon-matching of olfactory information. For example, if olfactory sensor410 detects olfactory information that does not substantially match anyolfactory signature of Table 2, an UNKNOWN PAINT message may bedisplayed to the user via user interface 152 and, optionally, trigger126 may be deactivated. Optionally, a notification may be transmitted toa remote server that the marking substance 134 in marking dispenser 122does not match any expected spectral signatures (i.e., a real-time alertto a supervisor that a user in the field may be spraying an unknownmarking substance), after which method 500 ends.

FIG. 6 is a flow diagram of a method 600 of operating marking device100. The method 600 is described with reference to the marking device100 shown in FIG. 1 and described above. The method uses one or more ofthe detection mechanisms described herein in a system for processingmarking substance information. By way of example, method 600 is anexample of using optical sensor 210 of FIG. 2 in one or more markingdevices 100 in a system for processing marking substance information.Alternatively, method 600 may be modified for marking devices 100 thatinclude olfactory sensors 410 of FIG. 4. Method 600 may include, but isnot limited to, the following acts.

In act 610, marking dispenser 122 is installed by the user in themarking device 100. By way of example, marking dispenser 122 may be anaerosol can containing a marking paint. Marking device 100 may includean optical sensor 210. Optical sensor 210 may be used to identify thecolor or any other characteristic of the marking substance 134 bycomparing detected spectral information with reference spectralsignatures of marking substances 134. In one example, optical sensor 210is installed in a marking device, such as the marking devices that aredescribed in the U.S. patent application Ser. No. 11/696,606 and U.S.patent application Ser. No. 11/685,602.

In act 612, the trigger 126 of the marking device 100 is pulled orotherwise activated by the user in order to dispense a quantity ofmarking substance 134 from the marking dispenser 122 onto the ground.The processor 150 receives an indication that the marking dispenser 122has been activated to dispense the marking substance 134.

In act 614, processor 150 instructs detection mechanism 140 to detectone or more characteristics of marking substance 134. For example,processor 150 may issue a command to detection mechanism 140 to detectmarking substance 134 in response to the user activating the trigger126. In one example, optical sensor 210 may be used to detect the colorand/or any other characteristic of marking substance 134. In anotherexample, olfactory sensor 410 may be used to detect the color and/or anyother characteristic of marking substance 134. The detector informationacquired by detection mechanism 140 is supplied by detection mechanism140 to processor 150.

In the embodiment where optical sensor 210 is used, spectral informationof marking substance 134 is supplied by optical sensor 210 to processor150. For example, the action of pulling trigger 126 of marking device100 to dispense marking substance 134 onto the ground may initiateoptical sensor 210. Optical sensor 210 measures the spectralcharacteristics of marking substance 134 that is dispensed from markingdispenser 122. Processor 150, executing detection algorithm 156,processes the detector information received from optical sensor 210 todetermine the color or any other characteristic of marking substance134. For example and referring to Table 1, a value of about 8 fromoptical sensor 210 corresponds to optical signature 0004, a value ofabout 18 from optical sensor 210 corresponds to optical signature 0009,a value of about 52 from optical sensor 210 corresponds to opticalsignature 0026, and so on. Subsequently, processor 150, executingdetection algorithm 156, generates output information to the user ofmarking device 100 indicating the type of marking substance 134 inmarking dispenser 122. For example, if optical sensor 210 detectsspectral information that substantially matches spectral signature 0009of Table 1, the brand, color, durability, and approved usage thatcorrelates with spectral signature 0009 (e.g., Brand #1, blue, mediumdurability, and water line) may be displayed to the user via userinterface 152. In this way, the user may verify immediately that theintended marking substance 134 (e.g., intended color or any otherattribute) has been installed in marking device 100.

In act 616, processor 150 performs initial processing of the detectorinformation received from detection mechanism 140 to provide one or moremarking substance characteristics. By way of example only, spectralinformation provided by optical sensor 210 may be processed to determinethe color of the marking substance being dispensed by marking dispenser122. The marking substance characteristics may be compared withreference information as described above to identify the markingsubstance 134. In other embodiments, the detector information receivedfrom detection mechanism 140 includes marking substance characteristicsand can be compared directly with the reference information. Thus, thedetector information received from detection mechanism 140 may includeinformation which requires initial processing by processor 150 toprovide marking substance characteristics and/or may include markingsubstance information without initial processing.

In block 618, acts involving utilization of the detector informationand/or the marking substance characteristics are shown. As used herein,“marker information” includes detector information and/or markingsubstance characteristics, or a selected subset of such information. Theacts shown in block 518 may be performed separately or in anycombination. The acts of block 518 may be performed or not performed,depending on the operating state and the application of marking device100. Also, additional acts may involve the marker information.

In act 618.1, the marker information is stored locally in storage device154 of marking device 100. The marker information can be storedseparately or with other data in an electronic record of a markingoperation or of operation of the marking device. The stored information,or a selected subset thereof, can be processed locally and/ortransmitted to a remote device for processing, can be displayed on adisplay device and/or an indicator, and/or can be used for real-timecontrol of the marking device, for example.

In act 618.2, the marker information is transmitted by communicationsinterface 158 to a remote device. Examples of the remote device include,for example, a computer located in the vehicle of the user or a remoteserver, or both. Communications interface 158 may utilize wirelesscommunication and/or a wired connection for transmission of the markerinformation. In one example of a wired connection, when the user returnsto his/her home base, the marking device may be connected by a wiredconnection to a central computing device. In particular, the markingdevice may be coupled to a docking station (not shown) that is designedto connect with the communications interface 158. The marker informationthat is stored locally within storage device 154 may be transmitted tothe central computing device.

In act 618.3, the marker information may be displayed to the user, forexample, on a display screen and/or by indicators. The markerinformation may be for information only or may require user action, suchas verifying that the marking dispenser is appropriate for the intendedapplication. The display of marker information provides feedback to theuser and permits verification that the intended marking dispenser 122has been installed.

In act 618.4, the marker information is used for real time control ofthe marking device 100. Thus, for example, selected marker informationmay be compared with reference information, for example, entered by theuser or downloaded to marking device 100. In the absence of a match,dispensing of the marking substance 134 from marking dispenser 122 maybe inhibited automatically. Other real-time control applications areincluded within the scope of the invention.

In act 620, a determination is made by processor 150 as to whether themarking operation is complete. For example, the user may indicate thatit is necessary to install another marking dispenser of the same colorin order to complete the marking operation or may indicate that anotherfacility is to be marked at the same site, thus requiring installationof a marking dispenser of a different color. When the marking operationis not complete, the process returns to act 610.

When the marking operation is complete, as determined in act 620, themarker information which has been stored in storage device 154 and/ortransmitted to a remote device is ready for offline processing. By wayof example only, offline processing may include compilation of data fora particular job site and/or determination of trends and statistics formultiple users. In another example, marker information may be processedfor the purpose of tracking the inventory of marking dispensers 122.More specifically, marker information may be processed in order toanalyze the usage of marking dispensers 122, such as, but not limitedto, the number of dispensers used and by which users. In a furtherexample, the marker information may be processed for the purpose ofquality control, such as to verify that the proper marking substanceshave been used in the assigned marking operations. The markerinformation is not limited to the uses mentioned above. The markerinformation may be used for any purpose (e.g., real-time productverification, tracking which user-location received which batch ofmarking paint, tracking marking paint inventory, tracking marking paintproblems, tracking marking paint usage, and so on).

FIG. 7 is a schematic diagram of the lower end of marking device 100,including a detection mechanism in the form of a weight sensor 710.Weight sensor 710 may be coupled, for example, to the end of markingdispenser holder 118 that is opposite spray nozzle 130 of markingdispenser 122, as shown in FIG. 7. Weight sensor 710 may be, forexample, any commercially available weight sensing device, such as anylow power, compact load cell device.

Weight sensor 710 may be mechanically coupled to marking dispenser 122such that marking dispenser 122 hangs freely therefrom. In one example,weight sensor 710 may be coupled to the lip of marking dispenser 122 viaa spring 712 and a hook 714 arrangement, such as shown in FIG. 7.Depending on the amount of marking substance 134 in marking dispenser122, marking dispenser 122 presents a variable load (as markingsubstance 134 is dispensed) that may be measured by weight sensor 710.The coupling of weight sensor 710 to marking dispenser 122 is notlimited to the arrangement shown in FIG. 7, and any coupling mechanismthat allows the variable load to be sensed by weight sensor 710 isacceptable.

In this embodiment, weight sensor 710 may be calibrated for both thefull and empty (or substantially empty) weight of marking dispenser 122in order to allow detection algorithm 156 to correlate the weight ofmarking dispenser 122 to the amount of marking substance 134 in markingdispenser 122. The relationship between the measured amount of markingsubstance 134 in marking dispenser 122 and the estimated markingdistance may be predetermined. Therefore, the weight of markingdispenser 122 may be further correlated to an estimated marking distancewhich the measured amount of marking substance 134 is capable ofmarking.

Table 3 below shows an example of reference weight information that maybe stored in storage device 154. The information correlates weight topercent (%) full and estimated marking distance. This correlation may bestored as predetermined weight signatures.

TABLE 3 Marking Substance vs. Expected Weight Signature Weight inMarking Distance ounces % Full in Feet Weight Signature 0 0 0 0000 1 0 00000 2 0 0 0000 3 5 50 0001 4 10 100 0002 5 15 150 0003 6 20 200 0004 725 250 0005 8 30 300 0006 9 35 350 0007 10 40 400 0008 11 45 450 0009 1250 500 0010 13 55 550 0011 14 60 600 0012 15 65 650 0013 16 70 700 001417 75 750 0015 18 80 800 0016 19 85 850 0017 20 90 900 0018 21 95 9500019 22 100 1000 0020

Referring to Table 3, weight signature 0000 is an entry that correlatesto marking dispenser 122 being empty or substantially empty of markingsubstance 134. By contrast, all other weight signatures (e.g.,0001-0020) are weight signatures of marking dispenser 122 containing atleast some usable quantity of marking substance 134. Based on Table 3, amessage may be displayed to the user via user interface 152 as to theamount of marking substance 134 in marking dispenser 122 and/or theestimated marking distance capability of marking dispenser 122.

Weight signature 0000 is useful to detect that a marking dispenser 122is becoming empty during a marking operation. For example, processor 150may detect that trigger 126 is being pulled and at the same time weightsensor 710 may detect a weight signature that substantially matchesweight signature 0000. This indicates that marking dispenser 122 isempty or substantially empty of marking substance 134. Because weightsensor 710 detects the weight of marking dispenser 122 rather thandetecting the marking substance 134 being dispensed, the weightmeasurement can be performed any time that a marking dispenser 122 isinstalled in the marking device. For example, the weight can be measuredwhen the marking substance 134 is being dispensed, upon installation ofa marking dispenser in the marking device, upon power up of the markingdevice, or at any other time.

In this embodiment, detection algorithm 156 may process and interpretweight information received from weight sensor 710 and then generate anappropriate response, if any. When in use, the movement and/or changingangle of marking substance 134 within marking device 100 may causereadings from weight sensor 710 to vary. Consequently, it may bepreferred to sample the output of weight sensor 710 and then processmultiple load measurements in order to determine the weight of markingdispenser 122.

An aspect of this embodiment is that weight sensor 710 may be used for:(1) determining in advance of or during a marking operation the amountof marking substance 134 in marking dispenser 122, and (2) detectingthat marking dispenser 122 is empty or substantially empty. By knowingin advance the amount of marking substance 134 in a full or partiallyfull marking dispenser 122, a user may better select a marking dispenser122 that is suited for the expected application. Additionally, theefficiencies that may be gained by knowing in advance the amount ofmarking substance 134 in marking dispenser 122 may cause the users to beless wasteful with marking dispensers 122.

Another aspect of this embodiment is that the user of marking device 100may be able to estimate in advance the number of marking dispensers 122required for a specified marking distance. For example, for a markingdistance of 3500 feet, knowing in advance that one full markingdispenser 122 can mark about 1000 feet, the user may have at least fourmarking dispensers 122 available (including the marking dispenser 122that may be already installed in marking device 100) upon beginning themarking operation.

As shown in Table 3, the weight of the marking dispenser indicates theamount of marking substance remaining and also indicates the estimatedmarking distance available with the marking dispenser. In otherembodiments, the estimated marking distance may be based on usage of themarking dispenser, as indicated, for example, by the distance alreadymarked with the same marking dispenser or the time of actuation of thesame marking dispenser.

In the embodiment described above, weight sensor 710 is used todetermine the amount of marking substance in the marking dispenser bycomparison of the detected weight with reference weight signatures. Inanother embodiment, weight sensor 710 can be used to determine if themarking dispenser 122 is empty or nearly empty by comparison of thedetected weight with a threshold value that represents the weight of anempty or nearly empty marking dispenser. The result of the comparisoncan be used to indicate that marking dispenser 122 is empty or nearlyempty.

Referring now to FIG. 8, a flow diagram of a method 800 is shown. Themethod uses marking device 100 which includes weight sensor 710 fordetermining the amount of marking substance in the marking dispenser.Method 800 may include, but is not limited to, the following acts.Additionally, the acts of method 800 are not limited to the followingorder.

In act 812, processor 150, executing detection algorithm 156, reads themeasured weight information (via weight sensor 710) of marking dispenser122 of marking device 100.

In act 814, processor 150, executing detection algorithm 156, determineswhether marking dispenser 122 is empty or substantially empty. Forexample, detection algorithm 156 determines whether the information thatis received from weight sensor 710 substantially matches weightsignature 0000 of Table 3. If yes, method 800 proceeds to act 816. Ifno, method 800 proceeds to act 818.

In act 816, processor 150, executing detection algorithm 156, generatesoutput information to the user of marking device 100. The outputinformation indicates that marking dispenser 122 is empty orsubstantially empty. The processor 150 performs any other desired tasks,such as, but not limited to, deactivating the trigger, transmitting anotification in real time to a remote server that marking dispenser 122is empty or substantially empty (i.e., a real-time alert to a supervisorthat a user in the field may be spraying but no paint is beingdispensed) and so on. For example, an OUT OF PAINT message may bedisplayed to the user via user interface 152 and trigger 126 may bedeactivated, after which method 800 ends.

If the marking dispenser is not empty, method 800 proceeds to act 818,wherein detection algorithm 156 compares in real time the measuredweight information that is received from weight sensor 710 with thestored weight signature information, for example, of Table 3. Morespecifically, detection algorithm 156 compares the measured weightinformation that is received from weight sensor 710 with, for example,weight signatures 0001 through n of Table 3 in order to determine amatch.

In act 820, processor 150 executing detection algorithm 156 generatesoutput information to the user of marking device 100 indicating thecharacteristics of marking substance 134. For example, if weight sensor710 detects weight information that substantially matches weightsignature 0009, the percent (%) full and marking distance thatcorrelates with weight signature 0009 (e.g., 45% and 450 feet) may bedisplayed to the user via user interface 152. Method 800 returns to act812.

FIG. 9 is a schematic diagram of the lower end of marking device 100,including a detection mechanism in the form of an out-of-paint sensor,such as a switch 910. Switch 910 may be coupled, for example, to the endof marking dispenser holder 118 that is opposite spray nozzle 130 ofmarking dispenser 122, as shown in FIG. 9. Switch 910 may be, forexample, any commercially available switch device, such as a push-buttontoggle switch. In this example, the push-button of switch 910 isoriented in the direction of marking dispenser 122.

Marking dispenser holder 118 may be mechanically coupled to markingdispenser 122 such that marking dispenser 122 hangs freely therefrom. Inone example, marking dispenser holder 118 may be coupled to the lip ofmarking dispenser 122 via a spring 712 and a hook 714. Depending on theamount of marking substance 134 in marking dispenser 122, markingdispenser 122 presents a variable load (as marking substance 134 isdispensed) that is supported by spring 712 and hook 714.

In this embodiment, the tension of spring 712 may be selected to providea known travel between marking dispenser 122 being full and being emptyor substantially empty. In particular, the tension of spring 712 may beselected such that when any usable quantity of marking substance 134 ispresent in marking dispenser 122, the body of marking dispenser 122 isnot in contact with switch 910 due to the weight of marking substance134 pulling downward on spring 712. By contrast, when marking dispenser122 is empty or substantially empty of marking substance 134, the bodyof marking dispenser 122 may come into contact with switch 910 becausethe weight of marking dispenser 122 is not sufficient to pull spring 712downward and away from switch 910. In this way, an out-of-paint sensormay be formed by use of switch 910.

An aspect of this embodiment is that switch 910 may be used as anout-of-paint sensor for detecting that marking dispenser 122 is empty orsubstantially empty. In this embodiment, detection algorithm 156 mayprocess and interpret the state of switch 910 in order to generate, forexample, an OUT OF PAINT message which may be displayed to the user ofmarking device 100 via user interface 152. Optionally, trigger 126 maybe disabled in the event of an OUT OF PAINT condition.

It is contemplated that the detection mechanism 140 of marking device100 and methods of the present invention may include optical sensor 210,olfactory sensor 410, weight sensor 710, switch 910 (i.e., anout-of-paint sensor), and any combinations thereof. The detectionmechanism 140 may directly detect the marking substance 134, as in thecase of optical sensor 210 and olfactory sensor 410, or may indirectlydetect marking substance 134, as in the case of weight sensor 710 andswitch 910. Furthermore, the detections mechanism 140 of marking device100 and methods of the present invention are not limited to opticalsensors, olfactory sensors, weight sensors, and out-of-paint sensors.Other types of sensors may be used for identifying the compositionand/or type of marking substance and/or determining whether the paintdispenser is becoming empty. In one example of determining whether thepaint dispenser is becoming empty, sound sensing devices may be used fordetecting the sound of marking substance 134 being sprayed from markingdispenser 122. In addition, marking device 100 may include more than onedetection mechanism of the same type or of different types. For example,marking device 100 may include two or more optical sensors or mayinclude an optical sensor and a weight sensor.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

What is claimed is:
 1. A marking apparatus to mark a presence or anabsence of an underground facility in a dig area, the marking apparatuscomprising: a housing configured to enable dispensing of a markingsubstance onto ground for marking the presence or the absence of theunderground facility in the dig area; a marking dispenser holder affixedto the housing to hold at least one marking dispenser; an actuatorcommunicatively coupled to the marking dispenser to cause the dispensingof the marking substance from the marking dispenser onto the ground inthe dig area; an optical sensor, coupled to the housing and disposedproximate to the marking dispenser, to provide sensor informationrepresentative of a color of the marking substance in the markingdispenser; and a processing device, coupled to the optical sensor, togenerate output information in response to the sensor information, theoutput information indicative of the color of the marking substance. 2.The marking apparatus of claim 1, further comprising a user interfacecoupled to the processing device, wherein the processing device providesselected information to the user interface based on the sensorinformation.
 3. The marking apparatus of claim 1, further comprising adisplay device coupled to the processing device, wherein the processingdevice controls the display device to display the output information. 4.The marking apparatus of claim 3, wherein the processing device isconfigured to perform an analysis of the sensor information and todisplay selected information on the display device based on theanalysis.
 5. The marking apparatus of claim 1, further comprising alocal memory coupled to the processing device, wherein the processingdevice controls the local memory to store the output information.
 6. Themarking apparatus of claim 5, wherein the processing device controls thelocal memory to record the sensor information in a table containingreference information.
 7. The marking apparatus of claim 1, furthercomprising a communication system coupled to the processing device,wherein the processing device controls the communication system totransmit the output information to a remote device.
 8. The markingapparatus of claim 7, wherein the processing device is configured toperform an analysis of the sensor information and to transmit anotification with the communication system based on the analysis.
 9. Themarking apparatus of claim 1, further comprising a light source, whereinthe light source is used in combination with the optical sensor toprovide the sensor information.
 10. The marking apparatus of claim 1,further comprising a switch sensor, coupled to the processing device, todetect that the marking dispenser is empty or nearly empty.
 11. Themarking apparatus of claim 1, further comprising a weight sensor,coupled to the processing device, to detect a weight of the markingsubstance in the marking dispenser.
 12. The marking apparatus of claim11, wherein the processing device is configured to determine an amountof marking substance remaining in the marking dispenser based at leastin part on the detected weight.
 13. The marking apparatus of claim 11,wherein the processing device is configured to determine an estimatedmarking distance available from the marking dispenser based at least inpart on the detected weight.
 14. The marking apparatus of claim 1,wherein the processing device: makes a comparison of informationrelating to the sensor information and reference information; andcontrols dispensing of the marking substance based on the comparison.15. The marking apparatus of claim 1, wherein the processing device isconfigured to determine an approved usage in response to the sensorinformation.
 16. A marking apparatus to mark a presence or an absence ofan underground facility in a dig area, the marking apparatus comprising:a housing; a marking dispenser holder affixed to the housing to hold atleast one marking dispenser; an actuator, communicatively coupled to themarking dispenser, to cause dispensing of the marking substance from themarking dispenser onto ground in the dig area; an optical sensor,coupled to the housing and disposed proximate to the marking dispenser,to provide sensor information representative of a color of the markingsubstance; a local memory configured to store reference information; aprocessing device, coupled to the optical sensor and the local memory,to compare the sensor information to the reference information and togenerate output information based on the comparison, the outputinformation indicative of the color of the marking substance; a displaydevice coupled to the processing device, wherein the processing devicecontrols the display device to display the output information; and acommunication system coupled to the processing device, wherein theprocessing device controls the communication system to transmit theoutput information to a remote device.
 17. A method of detecting a colorof a marking substance contained in a marking dispenser of a markingapparatus for marking a presence or an absence of an undergroundfacility in a dig area by dispensing the marking substance on ground,wherein the marking apparatus comprises a housing, a processing device,a memory containing reference information, the marking dispenser affixedto the housing and containing the marking substance, an actuatorcommunicatively coupled to the marking dispenser to cause the dispensingof the marking substance from the marking dispenser onto the ground inthe dig area, and an optical sensor coupled to the housing, the methodcomprising: A) acquiring, via the optical sensor, sensor colorinformation relating to the marking dispenser containing the markingsubstance; B) comparing, via the processing device, the sensorinformation to color reference information stored in the memory; C)determining, via the processing device, the color of the markingsubstance based at least in part on B); and D) generating outputinformation indicative of the color of the marking substance based atleast in part on C).
 18. The method of claim 17, wherein C) comprisesdetermining, via the processing device, the color of the markingsubstance based at least in part on a match between the comparison in B)of the sensor color information and the reference color information. 19.The method of claim 18, further comprising: E) inhibiting the dispensingof the marking substance in the absence of the match.
 20. The method ofclaim 17, further comprising: F) displaying the output information on adisplay device.
 21. The method of claim 20, further comprising: G)storing the output information into the local memory.
 22. The method ofclaim 21, further comprising: H) transmitting the output information toa remote device using a communication system.
 23. The method of claim17, further comprising: I) operating in a learning mode, includingacquiring, via the optical sensor, sensor color information relating acolor of a known marking substance and recording the detected color intothe memory containing color reference information.